NVE Illustrative Isolator Product Applications

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Isolators

Application Notes

Isolated PROFIBUS

NVE offers a unique PROFIBUS-compliant isolated RS-485 transceiver, the IL3685.

Extraordinary specifications include a 40 Mbps maximum data rate, up to 50 node fanout, and a 15 kV ESD rating for the bus nodes. The part provides transceiver and isolation functions in a single 0.3"-wide 16-pin SOIC package.

An illustrative PROFIBUS circuit is:

The 220 ohm termination resistor, along with another 220 ohm resistor and the other end of the bus, matches the bus impedance to minimize reflections. The 390 ohm "fail-safe" resistors guarantee a known state with no active transceivers. Bypass capacitors should be placed as close as possible to the appropriate IC.

Recommended application bulletins:

		AB-5: Isolated RS-485 and RS-422 (.pdf) Dramatically reduce chip count and board area with IL400- and IL3000-Series single-chip isolated transceivers.
		AB-6: RS-485 Systems (.pdf) Practical tips and rules of thumb for making RS-485 systems work.
		AB-19: PROFIBUS Compliance: A Hardware Design Guide (.pdf) Hardware design best practices for Profibus DP nodes. Covers three important but sometimes tricky design considerations: isolation, Profibus compatibility, and bus node polarity.

IL3685 product details

IL3685 data sheet (.pdf)

(N. America Only)